Sebum refers to lipid found in the human epidermis and is a mixture of a sebaceous secretion and the lipids derived from the epidermis, comprising triglycerides, fatty acids, wax esters, etc. In the human epidermis, 0.05 to 0.4 mg/cm2 of sebum is considered to be always present. Sebum moisturizes and softens the stratum corneum and also prevents external harmful substances and bacteria from invading and prevents substances such as water from being released out of the body. The amount of sebum varies depending on sites of the body, age, sex, the season, temperature, fat intake, etc. Generally, in humans, the sebum amount is known to be greater in men than in women, and is further abundant in fetuses and newborns, adolescents, and middle-aged to elderly men.
The sebum amount is an important factor to determine the skin type. The skin with a large amount of sebum is classified as oily skin, whereas the skin with a small amount of sebum is classified as not oily skin. When the oiliness increases, the skin becomes greasy, which gives an unpleasant feeling not only to the person him or herself but also to others. Also, when a sebum amount is excessive, sebum accumulates together with the stratum corneum inside the pores and may induce acne.
Accordingly, there is a need for a sebum secretion inhibitor which inhibits the sebum secretion. Although there are a variety of topical sebum secretion inhibitors, inhibition by an external medicine often fails to provide a fundamental solution, and there is a need for an orally administrable sebum secretion inhibitor. The orally administrable sebum secretion inhibitor is desirably comprising ingredients derived from food products or natural products to assure safety. Thus, the present invention provides a sebum secretion inhibitor comprising a collagen degradation product.
The following products are reported as orally administrable compositions for fine skin comprising food products or ingredients derived from natural products. Patent Literature 1 discloses a composition for fine skin and a hair growth formula containing as an active ingredient a polar solvent extract of kiwi fruit seeds. However, Patent Literature 1 does not mention the relationship between the active ingredient and the sebum secretion inhibition. Further, Patent Literature 2 discloses a preventive and therapeutic composition for psilosis and seborrheic skin diseases containing the extract of kiwi fruit. However, Patent Literature 2 mainly describes inhibition of psilosis and does not discuss the sebum secretion inhibitory effect in detail.
The following compositions are reported as orally administrable compositions for fine skin associated with collagen or degradation products thereof. More specifically, Patent Literature 3 discloses a composition for fine skin containing ingredients such as collagen, hyaluronic acid, etc., obtained by digesting skin of birds, etc., with protease, or the like. Patent Literature 4 discloses an orally administrable composition for promoting fine skin comprising collagen, and the like, and other substances. Patent Literature 5 discloses a composition containing a collagen hydrolysate. However, none of these literatures suggests or discloses the relation between collagen or a collagen degradation product and the sebum secretion inhibition.